The present invention relates to the field of bags having complementary closure strips designed to enable a user to perform a series of successive opening and closing operations.
Numerous types of bag and/or closure strip have already been proposed for this purpose.
By way of non-limiting example, reference can be made to the following documents: U.S. Pat. No. 4,929,255, U.S. Pat. No. 4,892,414, EP-0 562 774, EP-0 395 362, U.S. Pat. Nos. 5,382,094, 5,181,583, EP-0 728 665.
More precisely still, the present invention relates to the field of bags in which the closure strips are opened and closed by means of a slider.
Various types of bag and slider-operated closure strip have also been proposed.
By way of example, reference can be made on this point to the following documents: EP-0 051 010, EP-0 102 301, and EP-0 479 661.
Bags having slider-actuated closure strips offer the huge advantage, compared with bags that do not have a slider, of being easy to handle.
The slider makes it easier to separate the strips in order to open such bags, and conversely makes it easier to engage the strips in order to close such a bag. All that needs to be done for this purpose is to move the slider in translation along the strips.
Attempts have indeed been made to facilitate the handling of strips that do not have a slider, in particular by providing ribs on the walls of bags fitted in this way, the ribs making it easier to locate the strips by touch. Nevertheless, those dispositions do not give full satisfaction compared with slider-fitted bags. Firstly, making such ribs complicates the production installation. Secondly, such ribs do not provide location and actuation that are as easy as those provided by a slider.
However, in practice, it is observed nowadays that bags fitted with slider-actuated closure strips have not been the subject of major industrial development.
This seems to be due in particular to the fact that it is difficult to make use of slider-actuated closure strips on conventional machines for forming and/or filling bags automatically. Sliders gives rise to extra thickness which makes it very difficult for automatic machines to move strips and/or films fitted therewith.
As described in documents EP-0 051 010, EP-0 102 301, and EP-0 479 661, that is why proposals in the past have been made to add sliders to the strips after the closure strips have themselves been fixed on the film(s) making up a bag. However, those proposals generally require equipment that is rather complex for delivering the sliders, opening them, and then closing them on the closure strips, with the slider being accurately positioned relative to the closure strip, and as a general rule doing so on a continuous traveling line.
An object of the present invention is now to propose novel means for automatically making bags that include slider-actuated opening and/or sealing strips.
According to the present invention, this object is achieved by an automatic method of manufacturing bags that is characterized by the fact that it comprises the steps consisting in:
supplying at least one moving film adapted to form bag walls;
supplying at least one moving closure assembly comprising a W-shaped support sheet constituting both an internal channel-section tamperproofing tape provided on its facing internal surfaces with respective complementary closure strips, and also external lateral webs extending beyond the closure strips and the internal channel-section tape, the closure assembly also being prefitted with a series of sliders for actuating the closure strips and distributed along the length of the closure assembly as fed; and
fixing the closure assembly formed in this way, via the external lateral support webs to the film forming the bag wall.
As explained below, the method of the present invention makes it possible to eliminate the drawbacks of the previously-known means.
Firstly, because of the internal channel-section tamperproofing tape, the present invention makes it possible to guarantee initial sealing of the bags and makes it possible to inspect and spot easily any untimely opening or attempted opening of such bags.
In addition, and above all, because of the presence of the lateral external support webs which project considerably beyond the sliders, the present invention makes it possible to locate the sliders away from the fixing zone (preferably implemented by heat-sealing jaws) for fixing the closure assembly on the film constituting the bag.
The present invention also makes it possible to deliver bags either in the open state or in the closed state depending on requirements.
The present invention also relates to a machine for automatically manufacturing bags by implementing the above-specified method, and bags obtained thereby and to the closure assembly for performing the method.